The CREB (cAMP-response element binding) transcription factor is a stimulus-induced phospho-protein that is involved in numerous cell signaling pathways. Dysfunction and deregulation of CREB and CREB- interacting proteins cause human diseases such as cancer and neurodegeneration. CREB appears to play a key role in cell defense and survival in various tissues; however, the mechanisms through which CREB is involved in cell survival and the reason why deregulation of CREB function causes these human diseases remain incompletely understood. CREB phosphorylation at Ser-133 is the major posttranslational modification that enhances CREB activity in response to receptor-coupled stimuli. However, the status of CREB Ser-133 phosphorylation was not always correlated with CREB transcription function, suggesting that another event along with CREB Ser-133 phosphorylation seems to be involved in CREB regulation in a stimulus-specific manner. This research project may provide evidence and a critical answer to these unsolved problems because we recently found that HIPK2 (homeodomain interacting protein kinase 2), a genotoxic stress responsive kinase, activates CREB via phosphorylation of a new serine site (Ser-271) but not Ser-133, resulting in activation of CREB transcription function. We will test our hypothesis that HIPK2 is a new regulator of the CREB transcription factor via phosphorylation of this new CREB site that induces a cell survival program in genotoxic and oxidative stress conditions. The proposed experiments will focus on characterization of molecular mechanism through which CREB phosphorylation by HIPK2 activates its transcription function as well as downstream events including expression of target genes and cellular susceptibility to genotoxic stress in in vitro and in vivo models. The scientific impact of this research will be broad and significant because CREB regulates essential cellular events such as cell growth, differentiation, metabolism, and immune response. Therefore the unveiled new CREB regulation from successful completion of this proposal will enhance our understanding in various physiological and disease conditions closely associated with the CREB activity.